The present invention relates to closures for containers, and in particular, to a vented closure or cap arrangement for use with a filler neck of a fuel tank.
Internal combustion engines are typically provided with fuel tanks having a filler neck and a vented cap enclosing an opening at the end of the filler neck. During operation of the internal combustion engine, fuel is consumed in the engine and an additional measured amount of fuel is passed from the fuel tank to the carburetor for later combustion in the engine. Fuel tanks for internal combustion engines, and in particular, small fuel tanks of the type commonly used with gasoline powered lawnmowers, snowblowers, saws, and the like, must contain a venting mechanism to allow fuel to flow from the tank to the carburetor. During operation of the engine, the fuel tank is frequently subject to vibrations, increases in temperature or similar external stimuli which can result in an increase of pressure within the tank. Suitable venting means must be provided to relieve this pressure in order to assure continued smooth operation of the engine. If the tank is not properly vented, the increased pressure within the tank will force the fuel in the tank to seek the area of least resistance in order to lessen this pressure. This area of least resistance will generally be the carburetor, which will ordinarily result in an inefficient performance by the engine and possibly a flooding of the engine. Such an increase in pressure may also occur during non-use of the engine, such as during movement of the lawnmower, etc., or placing the item in an environment that is subject to occasional elevated temperatures.
While it is important to vent the tank, the venting mechanism must be constructed to allow air to enter and leave the tank but must not be so large as to allow fuel to splash out of the tank during movement and particularly during an inversion of the tank, such as may occur during use of a gasoline-powered saw. Similarly, as the level of fuel in the tank decreases due to the consumption of fuel by the internal combustion engine, a venting mechanism must be provided to allow air to enter the tank and occupy the space vacated by the fuel. If the vent does not properly permit the free entrance of air to replace the fuel, a partial vacuum may be created which may inhibit the supply of additional fuel to the engine. In some cases, this partial vacuum may cause a collapse of the walls of the fuel reservoir. Therefore, it is important to provide a venting mechanism that will vent gaseous vapors from within the fuel tank in order to relieve the internal pressure, as well as allow the outside air to vent into the tank to replace the fuel that has passed from the tank to the carburetor. At the same time, the vent must be constructed in a manner that prevents fuel from spilling during movement of the tank, and similarly, prevents external contaminants from entering the tank through the venting area.
Several prior art caps or stoppers that include a venting mechanism have been reported. U.S. Pat. Nos. 1,865,764 and 3,527,376 disclose stoppers and self-venting closures that include a cap having an aperture formed therein, and a slitted diaphragm that is seated in the cap. In each of these caps, the diaphragm acts as a release valve allowing the escape of internal gas pressure through the slit. The patents are directed to venting mechanisms that allow the release of internal pressure, however they do not specifically discuss venting bi-directionally, that is, allowing venting both into and out of the container. U.S. Pat. No. 3,406,862 discloses a venting closure plug for a container that includes a cylindrical diaphragm member having a slit centrally disposed in the resilient material of the end wall of the cylinder. The slit permits pressure within the container to be vented to the atmosphere, while preventing the escape of liquids from the container if the same is tilted or inverted. Similarly, outside air may be vented into the container. By varying the thickness of the side walls of the diaphragm, the closure plug can be constructed to vent into the container at a smaller pressure differential than is required for venting outwardly. The body of the plug includes inner and outer cup-shaped members disposed in telescoping relation to provide an internal cavity in which the diaphragm is positioned. Although this patent provides a mechanism by which the container may be vented both internally and externally, and also provides a mechanism to prevent the escape of liquids from the container when it is tilted, the particular construction of the plug, which requires inner and outer telescoped members as well as the diaphragm member results in a more complex structure of the plug than is desired, which similarly results in an increase in cost.
A fuel cap having a liner with two umbrella valves which permits bi-directional venting has also been used. One of the valves in this liner allows air to enter the fuel tank at a low pressure, and the other valve allows air to exit the container at a higher pressure. With this type of cap, the valves are held in place in the cap with an O-ring gasket and a hard plastic holder. Thus, it is necessary to have four separate pieces fitted within the inner surface of the cap to provide the venting mechanism.
It is desired to provide a vented cap arrangement to be used with a container such as a fuel tank, that is capable of venting vapors from within the container to the atmosphere, and likewise allowing the entrance of outside air to replace the fuel that has been drained from the tank. It is desired that venting of air into the tank occur at a lower pressure differential than venting of vapors from within the tank. It is also desired to provide a cap that will prevent the fuel or other liquid from splashing from the tank during movement, or to leak from the tank during tilting or inverting of the tank. Additionally, it is desired to provide such a closure that is simple in construction, has few parts, and is economical to manufacture.